Posted: Thu, Oct 14, 2010, 7:27 AM ET (1127 GMT)
An object initially thought to be a comet is instead likely the debris left by the collision of two asteroids. Hubble observations of the object, P/2010 A2, reveal a never-before-seen X pattern that astronomers believe resulted when an asteroid as small as 3 meters across struck the larger asteroid, about 120 meters across, vaporizing the smaller object and a cloud of debris swept into a tail by solar radiation. Astronomers believe that the impact actually took place in early 2009, but because of the objects' position in orbit relative to Earth it was not seen until early this year. Separate observations by ESA's Rosetta spacecraft, which observed P/2010 A2 on its way to a flyby of another asteroid earlier this year, support the impact hypothesis.